O2-Mediated Te(II)-Redox Catalysis for the Cross-Dehydrogenative Coupling of Indoles

Phenotellurazine redox catalysts: elements of design for radical cross-dehydrogenative coupling reactions

Redox active phenotellurazine catalysts have been recently utilized in two different cross-dehydrogenative coupling reactions. In this study, we revisit the design of the phenotellurazine redox catalysts. In particular, we investigate the level of cooperativity between the Te- and N-centers, the effect of secondary versus tertiary N-centers, the effect of heterocyclic versus non-heterocyclic structures, and the effect of substitution patterns on the redox catalytic activity.

Diversity-Oriented Synthesis of Indole-Fused Polycyclic Scaffolds via Rhodium-Catalyzed NH-Indole-Directed C-H Coupling of 2-Phenyl-1H-indoles with Propargylic Alcohol Derivatives

Diversity-oriented synthesis strategy for the efficient assembly of indole-fused polycyclic scaffolds via rhodium-catalyzed NH-indole-directed C-H coupling with propargylic alcohol derivatives in a regioselective manner was developed. Five 2-phenyl-1H-indole-embedded core skeletons were synthesized. In particular, three different indole-fused exo-olefin-containing polycycles were realized, which may be manipulated for further chemistry.

2-Benzamide Tellurenyl Iodides: Synthesis and Their Catalytic Role in CO2 Mitigation

Benzamide-derived organochalcogens (chalcogen=S, Se, and Te) have shown promising interest in biological and synthetic chemistry. Ebselen molecule derived from benzamide moiety is the most studied organoselenium. However, its heavier congener organotellurium is under-explored. Here, an efficient copper-catalyzed atom economical synthetic method has been developed to synthesize 2-phenyl-benzamide tellurenyl iodides by inserting a tellurium atom into carbon-iodine bond of 2-iodobenzamides in one pot with 78-95 % yields. Further, the Lewis acidic nature of Te center and Lewis basic nature of nitrogen of the synthesized 2-Iodo-N-(quinolin-8-yl)benzamide tellurenyl iodides enabled them as pre-catalyst for the activation of epoxide with CO2 at 1 atm for the preparation of cyclic carbonates with TOF and TON values of 1447 h-1 and 4343, respectively, under solvent-free conditions. In addition, 2-iodo-N-(quinolin-8-yl)benzamide tellurenyl iodides have also been used as pre-catalyst for activating anilines and CO2 to form a variety of 1,3-diaryl ureas up to 95 % yield. The mechanistic investigation for CO2 mitigation is done by 125 Te NMR and HRMS studies. It seems that the reaction proceeds via formation of catalytically active Te-N heterocycle, an ebtellur intermediate which is isolated and structurally characterized.

Synthesis of benzo[b][1,5]diazocin-6(5H)-one derivatives via the Cu-catalysed oxidative cyclization of 2-aryl-1H-indoles with 1,1-enediamines

A novel protocol for the synthesis of highly functionalized benzo[b][1,5]diazocin-6(5H)-one derivatives (BDCOs, 4 and 5) from 2-aryl-1H-indoles and 1,1-enediamines was developed via a complex cascade of reactions including regioselective free radical oxidation, the 1,2-addition of imine, imine-enamine tautomerization, intramolecular cyclization, and ring expansion. The cascade reaction was enabled by refluxing a mixture of two substrates in the presence of di-tert-butyl peroxide (DTBP) as an oxidant and anhydrous CuI as a catalyst in toluene under argon protection. Consequently, a series of BDCOs (4 and 5) were synthesized with high regioselectivity in good yield. This protocol can be used for the synthesis of functionalized BDCOs via a one-pot oxidative annulation reaction rather than a multi-step reaction, which is suitable for both combinatorial and parallel syntheses of BDCOs.